This project involves the longitudinal study of a group of 13-year-old rhesus monkeys and two generations of their progeny, all of whom live year-round in a 5-acre enclosure on the grounds of the NIHAC. The 13-year-old adults were all laboratory born, hand-reared in a nursery, and subsequently put together as a mixed-sex peer group. Despite the fact that none of these now middle-aged monkeys (nor any of their progeny) have had any physical exposure to any other monkeys, since they were first moved outdoors as juveniles they have consistently exhibited the full compliment of species-normative social behavior and group organization reported to date for rhesus monkeys born and living in feral environments. During the past year major modifications were made to the monkey shelter within the 5-acre enclosure, restricting observational data collection for a 5-month period. Nevertheless, those data that were collected continued to verify the species-normative behavioral patterns in the adults and ontogenic changes in the infants, the characteristic social organization of the troop along matriarchal lines, the species-appropriate changes in social rank among troop members, most notably the drop in dominance and eventual peripheralization of adolescent males, and the successful maternal care displayed by second-generation females. In addition, another infant born outside the group was successfully cross-fostered to one of the founder females who had just delivered a still-born infant, and a study investigating the manipulative skills of transmission of tool-use-like behavior as a function of age and matriarchal lineage was initiated. Plans for a second and third enclosure progressed, with data collection initiated on some of the monkeys who will be released into the new enclosures. Finally, collaborative arrangements with the Caribbean Primate Center (Sabana Seca, Puerto Rico) were initiated for the purpose of collecting parallel data on a feral rhesus monkey troop currently living in a similar multi-acre enclosure, in order to make direct comparisons with the present study group.